This invention relates to a device used with an optical fiber to diffuse light from a light-emitting end of the optical fiber to an object to be illuminated, heated or irradiated thereby. More particularly, the present invention relates to a tip for an optical fiber which is useful for diffusing the light from the optical fiber in a radial distribution pattern relative to the axis of the tip and along a length of the tip.
There are several methods that have been developed to obtain a cylindrical distribution of light energy from an optical fiber. One such method involves choosing a ratio of the indices of refraction between the outer transparent cladding and the core of the optical fiber so that internal reflection within the core is substantially less than total. The fiber thus obtained is a radiator rather than an internally reflecting transmitter and thus, allows light to radiate outwardly from the core and through the transparent cladding. The fiber produced by this method, however, has failed to provide a uniform output intensity distribution which is desirable for a variety of applications, such as the processing of materials in which the materials must be irradiated uniformly.
Other methods that have been developed for obtaining a cylindrical distribution of light include texturing the outer surface of the core, such as by acid etching the core, to produce a ground glass effect, embedding light scattering particulates near the outer surface of the core or throughout the cladding, and combinations of these alterations of the optical fiber. However, these alterations often weaken the fiber, thereby limiting the usefulness of the fiber in a variety of applications, such as those requiring a flexible fiber which is resistant to breakage.
U.S. Pat. No. 5,296,777, issued on Dec. 14, 1993 to Doiron et al., discloses a tip for an optical fiber comprising a silicone core which abuts the core of the fiber, a surrounding layer of silicone with scatterers dispersed therein, and an outer cladding of plastic tubing. With this tip construction, when the light from the optical fiber meets the silicone core of the tip, the light is dispersed rather than guided within the silicone core, whereupon light dispersed towards and entering the scattering layer is further dispersed before exiting the outer cladding. The scattering layer is modified in terms of the arrangement and concentration of scatterers embedded therein to obtain a desired intensity distribution of the light diffused by the tip. However, as light is dispersed in the core as well as the scattering layer of the tip, modification of the scattering layer is an inadequate means of controlling the intensity distribution profile of the light diffused by the tip.
It is a primary object of the present invention to provide a light-diffusing tip for an optical fiber which provides light on the surface along the length of the tip useful for illuminating, heating or irradiating a targeted object.
It is another object of the present invention to provide a method of using such a light-diffusing tip, such as a method of inserting the light-diffusing tip into a targeted object and providing light on the surface and along a length of the tip sufficient to illuminate, to heat or to irradiate the targeted object.
Further objects of the present invention include providing an apparatus incorporating such a light-diffusing tip and providing a method of producing such a tip.